Nachman Garber

On the specificity of the d-galactose-binding lectin (PA-I) of Pseudomonas aeruginosa and its strong binding to hydrophobic derivatives of d-galactose and thiogalactose

The D-galactose-binding lectin (PA-I) from the bacterium Pseudomonas aeruginosa, isolated by affinity chromatography on Sepharose, was examined for its relative affinities for simple sugars and their derivatives using equilibrium dialysis and hemagglutination inhibition tests. The lectin, which was found to bind 0.68 mol of D-galactose per subunit of 12.8 kDa, exhibited an association constant (Ka) of 3.4 x 10(4) M-1 for D-galactose and higher affinities for hydrophobic and thio derivatives of D-galactose (with highest affinity for the hydrophobic thio derivatives). alpha-Methyl-galactoside was a stronger inhibitor than the beta-methyl derivative and alpha-lactose was a weak inhibitor but the hydrophobic phenylated derivatives of the beta-configuration of D-galactose were more potent inhibitors than the respective alpha-galactosides.

‘Subinhibitory’ Erythromycin Represses Production of Pseudomonas aeruginosa Lectins, Autoinducer and Virulence Factors

Pseudomonas aeruginosa infection is preceded by selective adhesion of the bacteria to the host target cells via diverse adhesins, including lectins. This step enables maximal damage to the target host cells by the bacterially secreted injurious toxins and enzymes. The production of both lectins and many of the virulence factors is positively controlled by transcription activators including signaling autoinducers (N-acyl-L-homoserine lactones). We show in this communication that erythromycin at subminimal growth inhibitory concentrations simultaneously suppresses the production of P. aeruginosa hemagglutinins (including lectins), protease, hemolysin and homoserine lactone autoinducers. The antibiotic-treated bacteria also show reduced virulence to mice, endorsing clinical observations that indicate the efficiency of low-dose erythromycin treatment of persistent drug-resistant P. aeruginosa infections.

Purified Pseudomonas aeruginosa PA-I lectin induces gut growth when orally ingested by rats

The effects of PA-I lectin isolated from the human pathogen Pseudomonas aeruginosa upon cellular metabolism in vivo have been studied using the rat gut as a model system. Orally ingested PA-I lectin stimulated metabolic activity and induced polyamine accumulation and growth in the small intestine, caecum and colon. The nature and extent of the changes induced by PA-I lectin were similar to those caused by dietary kidney bean lectin and were likely to lead to impaired epithelial cell function and integrity. This finding contributes to our understanding of the possible roles of these lectins in Pseudomonas aeruginosa infection.

Pseudomonas aeruginosa PA-I lectin gene molecular analysis and expression in Escherichia coli.

This communication describes a Pseudomonas aeruginosa DNA fragment (cloned in lambda gt11) which contains the structural gene coding for the galactophilic PA-I lectin (pa-1L, 369 bp) and an additional downstream 237 bp sequence. This DNA is relatively rich in G + C (54%), and exhibits a strong codon preference biased for XXC and also for XXG. The Shine-Dalgarno site of the gene is preceded by an adjacent ATATAT sequence resembling the -10 sequence of the Escherichia coli promoter. The stop codons are followed by a stem and loop structure--typical of the rho-independent transcriptional stop element. This lambda gt11-cloned DNA was expressed in E. coli Y1090 cells. The resulting cell lysates exhibited a galactose-specific hemagglutination and a protein with electrophoretic mobility similar to that of the native PA-I, which were both absent from E. coli lysates infected with ovalbumin gene-bearing bacteriophages. The recombinant PA-I, purified by gel filtration and affinity chromatography, was shown to be a galactophilic hemagglutinin resembling the native lectin in molecular weight and selective reactivity with rabbit anti native PA-I serum. These results are important for development of a safe Pseudomonas aeruginosa vaccine using recombinant DNA techniques, thus avoiding contamination with toxic products of this bacterium.

The Five Bacterial Lectins (PA-IL, PA-IIL, RSL, RS-IIL, and CV-IIL): Interactions with Diverse Animal Cells and Glycoproteins

Among the ten different lectins discovered in the old biochemistry laboratory at Bar-Ilan University during the years 1972–2006 (Fig. 9.1), five were isolated from three soil bacteria: Pseudomonas aeruginosa (PA) [1–3], Ralstonia solanacearum (RS) [4, ], and Chromobacterium violaceum (CV) [6].

Abrogation of the resistance of choline-induced Pseudomonas aeruginosa virulence to sub-MIC erythromycin by ethanol

Despite Pseudomonas aeruginosa antibiotic resistance, erythromycin (ERM, a macrolide) at subinhibitory concentration (sub-MIC) reduces its pathogenicity. We assessed ERM effects on P. aeruginosa in cultures containing choline (Ch) without and with 1% ethanol (Et) addition. Ch, as an osmoprotectant, increases the following virulence factors (VIFs): lectins (haemagglutination); proteases (casein and elastin lysis); haemolytic phospholipase C (PLC-H; haemolysis); pyocyanin (pigment o.d.) and autoinducers (violacein bioassay). Ethanol also increases lectins, proteases, pyocyanin, autoinducers and rhamnolipid (RHAL; haemolysis) formation, but reduces Ch-induced PLC and protease (elastase) activities. ERM has been shown to totally suppress the Et-induced VIFs, whereas partially reducing the Ch-induced ones. Unexpectedly, ERM combination with 1% Et dramatically annuls the Ch-induced factors. Et contribution might be attributed to its effect on cell membrane, displaying synergism with ERM, whereas antagonizing Ch osmoprotective potential and shifting gene expression. This information is worth further molecular investigation and clinical consideration for skin infection therapy.

Regulation of Lectin Production by the Human Pathogens Pseudomonas aeruginosa and Chromobacterium violaceum : Effects of Choline, Trehalose, and Ethanol

The worldwide-distributed Pseudomonas aeruginosa (PA) and the geographically restricted (confined to tropical and subtropical zones) Ralstonia solanacearum and Chromobacterium violaceum are Gram-negative proteobacteria that dwell in soil and water. They are essentially beneficial saprophytes that vigorously decompose plant and animal remnants and organic debris, contributing to world carbon and nitrogen cycling (Fig. 11.1). In accordance with their distinguished role in nature, these bacteria are endowed with very prosperous arsenals of cell-binding adhesins, toxicating proteinaceous and nonproteinaceous factors, and hydrolytic enzymes as virulence factors (VIFs), enabling them to home in on dead or damaged cells and molecules and attack them.